Fluxmeter



Jan. 18, 1949. v, RUSSELL I 2,459,341

FLUX METER Fild Aug. 13, 1945- I 2 Sheets-Sheet 2 I ifi 53 381/4 .Z ETZZ U Valardn Zeus Z Patented Jan. 18, 1949 UNITED STATES PATENT OFFICE FLUXMETER Valoran Russell, Morton Grove, Ill.

Application August 13, 1945, Serial No. 610,610

7 Claims. (Cl. 175183) The present invention relates to a flux meter and more particularly to a means for and a method of indicating the relative strength of a permanent magnet.

An object of the present invention is to provide a simple and effective means for determinin the magnetic flux produced in a non-magnetic gap by a permanent magnet.

Another object of the invention is to provide a method of determining the magnetic energy of permanent magnets.

A further object of the present invention is to provide a novel testin apparatus for determining the magnetic flux produced by a permanent magnet in the air gap of a radio loud speaker in which the relatively movable parts are held against accidental displacement during a test.

The present invention will herein be described as means for and method of indicating the flux density established in the air gap of a permanent magnet speaker, although the invention is not to be limited to such,

Generally speaking, the invention contemplates the reciprocation or straight line oscillation of a coil having a known stroke and known speed in the air gap of a permanent magnet, and measuring the current developed in the coil.

An embodiment of the invention is illustrated in the accompanying drawings and the views thereof are as follows:

Figure 1 is a side elevational view of an apparatus for practicing the invention;

Figure 2 is a front elevational view of the apparatus;

Figure 3 is a front view of a part of the apparatus showing guide plates and in section a speaker unit, together with a table for supporting the unit while undergoing tests;

Figure 4 is a fragmental enlarged sectional view taken in the plane of line IVIV of Figure 3; and

Figure 5 is an enlarged section taken in the plane of line VV of Figure 1.

The drawings will now be explained.

Referring to Figures 1 and 2, I designates a base from which rises a rear post having a head formed by a forwardly projecting part l2. The post II is fastened to the base by suitable brackets l4 through which screws l pass for engaging the post and the base. Fastened to the front end of the member I2 is a downwardly extending plate l6, of metal,shown, in Figure 4, as having a V groove ll formed in its front face.

Above the groove the plate has an aperture l3,

2 the groove extending from the aperture l8 to the lower margin of the plate.

Mounted on the head and attached to the member I2 is a constant speed electric motor IS the shaft of which carries an eccentric 20 movable within the aperture l8 of the plate. The motor shaft is designated as 2|.

Within the aperture is a yoke 22 within which the eccentric 20 works to oscillate the yoke in a vertical direction. A rod 23 has its upper end secured to the yoke 22. The rod is square in cross section with two opposite margins 24 milled flat, leaving two opposite square edges 25 and 26. The rod rests in the groove [1 with its edge 25 against the bottom of the groove. A cover plate 21 is formed with a V groove 28 on its inner surface which receives the edge 26 of the rod when the plate is fastened against the face of plate l6, as is shown in Figures 3 and 4. The grooves in the plates l6 and 21 provide a guideway for the rod which permits endwise reciprocation but which prevents any tendency to turn or rotate. The plate 21 is fastened in place by screws 29 threaded into the plate I6.

A front post l3 rises from the base Ill but is shorter than the rear post II. The post I3 is provided with a guideway 30, vertically disposed, for a rack bar 3| carrying a rack 32, J'ournaled in bearings 33 and 34 carried by the post [3 is a pinion shaft 35 carrying a pinion 36 enmeshed with the rack 32. A handwheel 31 is fastened to an end of the shaft 35 for rotating the pinion to move the rack. The upper end of the rack bar 3| carries a table 38 in the center of which is a depression 39, for a purpose to be later explained.

The post and pinion are shown as arranged within a U-shaped casing body the lower end of which rests on the base l0 and the margins of which are fastened to the rear post II by screws 4|. An angle bracket 42 fastens the casing to the base I0 and post l3 by screws 43.

Inasmuch as the rack bar should be held in selected positions while a magnet is being tested, a friction brake means is provided. The brake means here illustrated includes a screw 44 threaded through the wall of the casing 40 and carrying a shoe 45 which bears against the rack bar 3|. By moving the screw inwardly the shoe will engage the bar to frictionally hold the bar with a selected degree of resistance so that the bar may be raised or lowered, by positive manipulation of the handwheel 31, but will not fall when the handwheel is released.

While the screw 44 is illustrated as having a [9. A line wire 48 leads from the condenser to' one side of the electrical supply circuit. A wire 49 leads from the motor H! to a motor control switch 50, which is mounted on the casing 40. .A wire leads from the switch 50 to the other .side of the supply line. The switch 50 is a snap M toggle switch to open and close the line circuit to the motor I9.

The radio speaker unit to be tested, as shown in Figure 3, includes a permanent ma'gnet52 fastened to a keeper or yoke 53 by means of a bolt 54. This yoke 53 provides a return flux path for the permanent magnet 52. The bolt 53 secures a soft iron core or post 55 to the upper end of the permanent magnet so that the post will "lie within the air gap 56 formed in the yoke 53. Thus the post 55 also forms part of the flux path and, to-

gether with the yoke 53, causes substantially all of the mmf. drop to occur across the gap. The basket or diaphragm support 51 is fastene'dto the yoke as by spot welding.

H In "the finished speaker unit a voice "coil (not shown) is carried by a 'di'aphragmK'n'ot shown); spann ng the mouth of the basket '51. This vo ce coil surrounds the post '55 in the gap 56 of the keeper '53 in spaced relation to the post and keeper. The coil is energized by an amplifier cir cuit and acts "as a motor to vibrate the dia} In the testing of the speaker unit acco'r'c'l'ing 'te this invention, an inverted cu'p 58 is carried y 'therod'23. This cup has a'coil 59 of wire wound therearound. The terminal ends 59a and 59b of the coil 5Q hug the cup so that they will h'ot (contact the keeper or post. I

Mounted on the head 12 is a meter 6'! which :may be a voltmeter. Attached to the rear race of the plate It is a terminal 'block 62 hem which :wires 63 and 54 lead to the voltmeter "6]. terminal erids'59a and 59b of coil 59 are coninected respectively to the wires '63 and E ton the terminal block.

To place a speaker unit on the 'table lower the table. A speaker unit is thenplaced on the table with the head of the bolt 54 in the recess "39 of the table, thus centering the unit. The handwheel 31 is then reversely rotated to raise the table until the cup is entered in the air "gap 56 of the keeper, in the position shown in Figure 3. The friction brake efiect on the bar 3| will hold the table in selected position and the operator manipulates motor switchSU whereuponthe con 1160 stant sp'eed motor reciprocates or oscillates the rod 23 and with it the cup 58 and coil 59'which movement ofthe cup drives the coil'toact as a generator cutting the lines'of force in the air gap and generatin a current in the coitwhich current is then carried by the'conductors 59a and 5% to the terminal block"62' and to'the voltmeter 6! where an exact reading may be had'ofthe voltage generated in the magnet by the'reci-proc'ation' or oscillation of the voice coil.

It will be noted that to rnakethis test; afreplic'a of a speaker voice coil-is operated as afg'erierator to induce an E. M. F. which "can 'be'indicated in the meter. Since the speed andstroke of the coil 'i5 known and constant, the generated voltage gives The I 3 3 for 'test, the handwheel 3? is rotated manually to can *at Substantially a constant ate ane to receive said first "c'oil marsmagnemc force inthe air'fgap thus settinghp a' current which cah be read exactly on the "meter;

The invention has been described herein more or less precisely as to details, yet it is to be understood that the invention is not to be limited thereby, as changes may be made in the arrangement and proportion of parts, and equivalents may be substituted,without departing from the spirit and scope of the invention.

I claim as my invention: 1. In apparatus for determining the density' in the air gap or a-=pe'rmanent=magnet speaker co ripri'sing means -{for "supporting a permanent magnet'speaker and voice coil removed, mean moved voice coil, means ro said "simulating ineans i W speaker" through -a substantially fcons't and. at a substantiallyconstantfrequenc means I responsive to the effe ive tame 'du'ced voltage in said s'imul' eating the relative flux dens 2. Apparatus formeasurihg'theefiect 1 netic energ of a permanent magnet speaker comprising means 'for suppor tin'g the "yoke n'd magnet of a per'inanentinaght spe'aker in normal-relationship, a'ecirmcumea for-reap cation s ubst ahtiallyat right angles to' the p time {of its awn race and in w the air gap betwe n yoke and-magnet, means for reciprocal-tings substantially -'a constant str'ok measuring the electromo nu ihea'ns force induced in "'To'rce Said con, the intensitys'o induced being a fu'nct n of" said =rod, 'said "guide'rnea'ns and rod halvingoperating parts Tor -"allowing 're'ciprocable' move- --ment of'the rod but pre'veri ting" rotation" cr i t, a

voice coil on said rod, a driving connecti tween :said motor "and said frod arran'ged to reciprocate said rod through' a "substantially constant stroke a vertically adju'stable table for' r'eceiving and sup'portin'g a "speaker unit for test, means for vertically adjusting thetablameans for locking the table in adjusted" position 'during test, means for operating the motor-to vibrate the voice coil as a generatoiyand a meter fo'r'indicating the current developed by the vibration ofthecoil.

4. In an apparatus of theclass described, a

constant speed motor, a rodlinearly reciprooa'ble by the motor shaft through-a substantially cone stant stroke, a coilon said rod simulatingthe jvoi'ce coil of a dynamic 'spe'aken a dynamic "speaker unit'with' its vofice can removed mou ted air 'gap, and a meter'e1ecti'icaliy cornice saianrst coil -to 'iiidicate'ttie efieetive valueflof "the voltage nduc'ejd infsaid first a r by reciprocation thereof.

5. In an apparatus of the class described, a base, an upright post thereon having a head overlying the base, said head supporting a vertical plate with an aperture in it and a vertical V-groove extending down from said aperture to the lower margin of the plate, a constant speed motor supported by said head With its shaft extending into said aperture, an eccentric on said shaft, a yoke about said eccentric to be reciprocated thereby, a rod connected at its upper end to said yoke and having two oppositely disposed edges arranged with one edge in said V-groove, a cover plate having a vertical V-groove in it against said plate and overlying the rod and receiving the other rod edge in its groove, a voice coil connected to the lower end of said rod, 2, table below said head to support a speaker unit for test, a speaker unit on said table movable thereby to position the air gap in its keeper about said voice coil, means for vertically moving said table, means for locking said table in adjusted position, a switch for said motor, and a meter electrically connected to the voice coil Winding to indicate the current developed as the voice coil is reciprocated by said motor.

6. In an apparatus of the class described, including a base, a rear post rising from the base and having a head overhanging the base, a front post, a rack vertically reciprocable in said front post, a table on said rack, a pinion for moving said rack, a handwheel for operating said pinion, a brake for holding said rack bar against movement, said head carrying a substantially constant speed motor and a vertically reciprocable rod, a driving connection between said motor and said rod arranged to reciprocate said rod through a substantially constant stroke means guiding said rod to prevent rotative movement thereof, said table being lowered to receive a speaker unit on it and raised to bring the air gap of the speaker about said voice coil, and means for indicating the current developed by reciprocation of said voice coil in said air gap.

'7. In an apparatus of the class described, a base, a post rising from the base and having a head overlying the base, a substantially constant speed motor supported by said head, a vertically reciprocable rod supported and guided in said head, an eccentric connected to one end of said rod, said motor having its shaft connected for driving the eccentric, means guiding said rod in straight line reciprocable movement while preventing rotative movement thereof, a voice coil connected to the other end of the rod, means for moving a dynamic speaker unit in the direction of length of the rod to position the magnetic circuit air gap thereof to receive said coil, means centering said speaker unit on said moving means, means for locking said moving means in adjusted position, means for operating the motor to reciprocate the coil, and a meter electrically connected to the coil winding to indicate the voltage induced in said coil by the reciprocation thereof.

VALO'RAN RUSSELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name- Date 1,270,100 Ballman June 18, 1919 1,662,433 Murray Mar. 13, 1928 2,135,843 Pye Nov. 8, 1938 2,231,085 Morrison et a1 Feb. 11, 1941 2,231,810 Kamenarovic Feb. 11, 1941 2,382,743 Penther et al Aug. 14, 1945 

